Line an 20cm square pan with baking parchment and preheat the oven to 180°C.
Put the coconut oil and 1 cup dark chocolate in a heatproof bowl. Set a saucepan with 4cm water over a medium-low heat and bring to a simmer. Place the bowl over the pan, making sure the bottom of the bowl doesn’t touch the water. Stir until melted, then set aside to cool.
Pour the aquafaba and sugar into a large bowl and beat with an electric hand whisk until stiff peaks form. This should take 4-5 minutes.
Stir together the flour, salt and baking soda.
Mix the cooled melted chocolate mixture into the aquafaba (drained chick pea water). Fold in the dry ingredients and coffee, being careful not to over work the mixture. Stir through the remaining chopped chocolate.
Pour into the prepared tin. Put the peanut butter in a small bowl and microwave for 30 seconds. Spoon dots of peanut butter over the top of the brownies, then use the end of a spoon to swirl across the surface.
Bake for 20-22 minutes or until a toothpick inserted into the centre comes out clean. Slice into 12 squares to serve.